I had a Beta Lead 410 combo that I played bass through, and it sounded OK. The reverb was interesting also, never got too loud with it. The open back 410 cab with guitar transducers was the limiting factor, the amp worked fine with bass. Never had the opportunity to A/B a Beta Bass and a Beta Lead though.
I'm not familiar with the Beta series in particular, but, generally speaking, there is no problem with using a guitar head for bass. Guitar speakers are more problematic, but if the head gives you a sound you like, go for it. I, myself, have frequently used Sceptre and Sentura II heads (essentially the same) for bass, with good results.
??